# for manage page
gem 'activeadmin', github: 'activeadmin'

$ bin/rails g active_admin:install --skip-users
      create  config/initializers/active_admin.rb
      create  app/admin                             # ActiveAdmin で編集させたいリソース毎にファイルを設置するフォルダ
      create  app/admin/dashboard.rb                # ログイン後のダッシュボードのページ
       route  ActiveAdmin.routes(self)
    generate  active_admin:assets
      create  app/assets/javascripts/active_admin.js.coffee
      create  app/assets/stylesheets/active_admin.css.scss
      create  db/migrate/20150218033243_create_active_admin_comments.rb

$ bin/rake db:migrate

  config.site_title = 'hoge'                               # サイトのタイトル
  config.site_title_link = '/manage'                       # ロゴのリンク設定
  config.site_title_image = '/assets/hoge_logo.png'        # ロゴの画像を用意
  config.default_namespace = :manage                       # route がデフォルトの /admin ではなく、/manage になる
  config.namespace :manage do |manage|
    manage.site_title = 'hoge 管理ページ'
  end
  config.favicon = '/assets/favicon.ico'                   # favicon を用意できたら
  config.authentication_method = :authenticate_admin_user! # 管理画面にアクセスする際の認証メソッド ( concerns に追加するメソッド )
  config.current_user_method = :current_admin_user         # ログインユーザー情報を取得するメソッド ( concerns に追加するメソッド )
  config.logout_link_path = :destroy_admin_session_path    # ログアウト時のパス 新たに定義する routes
  config.logout_link_method = :delete                      # ログアウト時の METHOD を DELETE へ

  ActiveAdmin.routes(self) # active_admin:install に自動的に追加されてる
  scope :manage do
    get :login, to: 'users#new_admin_session', as: :new_admin_session
    post :login, to: 'users#create_admin_session', as: :create_admin_session
    delete :logout,to: 'users#destroy_admin_session', as: :destroy_admin_session
  end

module AdminUserAuthenticationAction
  extend ActiveSupport::Concern

#  include する UsersController とかに before_action が入っていた場合は、下記の様な感じで skip するようにする
#  self.included do
#    skip_before_action :authenticate_by_token, only: [:new_admin_session, :create_admin_session, :destroy_admin_session]
#  end

  def new_admin_session
    redirect_to manage_root_path if current_admin_user
    render template: 'users/admin_session/new' # view は users に別途フォルダをわけて作成した
  end

  # session 情報に、ログイン者の情報を追加
  def create_admin_session
    begin
      @current_admin_user = User.admin_authenticate_by_email(params[:user][:email], params[:user][:password])
      session[:admin_user_id] = @current_admin_user.id
      session[:admin_session_expires_at] = 60.minutes.from_now # セッション保持期間は 1 時間
      redirect_to manage_root_path
    rescue User::LoginFailed
      redirect_to new_admin_session_path
    end
  end

  # ログアウト処理
  def destroy_admin_session
    if current_admin_user
      session.clear
    end
    redirect_to new_admin_session_path
  end
end

module AdminUserAuthenticationFilter
  extend ActiveSupport::Concern
  class AdminUnauthenticated < StandardError; end

  self.included do
    rescue_from AdminUnauthenticated do
      redirect_to manage_root_path
    end
  end

  def authenticate_admin_user!
    redirect_to new_admin_session_path unless current_admin_user
  end

  # active admin から呼ばれるログインしたユーザーを取得するメソッド
  def current_admin_user
    if session[:admin_user_id] && session[:admin_session_expires_at].try(:>, Time.zone.now)
      session[:admin_session_expires_at] = 60.minutes.from_now
      begin
        # Enumerize で role が admin のユーザーを検索
        @current_admin_user = User.with_role(:admin).find_by!(id: session[:admin_user_id])
        session[:admin_user_id] = @current_admin_user.id
      rescue ActiveRecord::RecordNotFound
        raise AdminUnauthenticated
      end
    else
      @current_admin_user = nil
    end
    @current_admin_user
  end
end

class ApplicationController < ActionController::Base
  include AdminUserAuthenticationFilter # include しておく

  # 色々な処理
  # 色々な処理
end

class UsersController < ApplicationController
  include AdminUserAuthenticationAction # include しておく

  # 色々な処理
  # 色々な処理
end

class User < ActiveRecord::Base
  class LoginFailed < StandardError; end

  extend Enumerize
  enumerize :role, in: { user: 1, admin: 2 }, default: :user, predicates: true, scope: true

  belongs_to :prefecture # 都道府県

  validates :email, :name, :prefecture, :address, presence: true

  scope :active, -> { where(deleted_at: nil) }

  def self.admin_authenticate_by_email(email, password)
    user = self.with_role(:admin).find_by!(email: email)
    user.authenticate(password) or raise LoginFailed # Devise は使ってないので、標準の authenticate を使用
  rescue ActiveRecord::RecordNotFound
    raise LoginFailed
  end
end

:sass
  #login_form
    width: 40%
    margin: 30px auto
    label
      margin-bottom: 5px
  #user_email, #user_password
    width: 100%
    margin-bottom: 5px
  input
    box-sizing: border-box
    &[type="submit"]
      width: 30%
  .actions
    text-align: center

= stylesheet_link_tag "active_admin"
= form_for :user, url: create_admin_session_path, :html=> {:id => 'login_form'}, method: :post do |f|
  .field
    = f.label :email
    %br
    = f.email_field :email, autofocus: true
  .field
    = f.label :password
    %br
    = f.password_field :password, autocomplete: "off"
  .actions
    = f.submit "ログイン"

$ bin/rails g active_admin:resource User

ActiveAdmin.register User do
  config.per_page = 15 # 一覧ページのページングの件数

  # 一覧ページの検索条件
  filter :id
  filter :role
  filter :email
  filter :name
  filter :prefecture # 自動で Prefecture#name の select タグが表示される
  filter :address
  filter :deleted_at
  # 上記検索条件に表示する項目を remove_filter で書くと下記のようになる
  # remove_filter :crated_at, :updated_at

  # 一覧ページ
  index do
    column :id
    column :role
    column :email
    column :name
    column :prefecture # 勝手に prefecture.name を表示
    column :address
    column :deleted_at

    actions 
  end

  # 詳細ページ
  show do
    attributes_table do
      row :id
      row :role
      row :email
      row :name
      row :prefecture # 勝手に prefecture.name を表示
      row :address
      row :deleted_at
    end
  end

  # 新規作成/編集ページ
  form do |f|
    inputs  do
      input :role
      input :email
      input :name
      input :prefecture
      input :address
    end

    actions
  end

  permit_params :role, :email, :name, :prefecture, :address # 更新可能な attribute を記載
end

config.display_name_methods = [:email]

show title: :name do
  row: :id
  row :name
end

ActiveAdmin.register User do
  actions :index # index だけ可能

  ....
end

ActiveAdmin.register User do
  actions :all, except: [:edit, :update]

  .... 
end

ActiveAdmin.register User do
  scope 'Active', :active # User に定義された scope 
  scope('ユーザーのみ') { |scope| scope.with_role(:user) } # with_role は Enumerize で追加された scope
  .... 
end

ActiveAdmin.register User do
  scope 'Active', :active, default: true

  .... 
end

ja:
  formtastic:
    :yes: 'はい'
    :no: 'いいえ'
    :create: '%{model}を作成'
    :update: '%{model}を更新'
    :submit: '%{model}を投稿'
    :cancel: '%{model}を中止'
    :reset: '%{model}を初期化'
    :required: '必須'

index do
  column :role do |user|
    user.role_text # or user.role.text
  end
end

show do
  column :role do |user|
    coupon.role_text # or user.role.text
  end
end

filter :role, as: :select,
  collection: User.role.values.map { |value| [User.role.find_value(value).text, User.role.find_value(value).value] }

input :role, as: :select,
  collection: User.role.values.map { |value| [User.role.find_value(value).text, User.role.find_value(value).value] }

form do |f|
  inputs  do
    input :image, as: :file, input_html: { accept: 'image/*' }
  end
end

form do |f|
  inputs do
    input :start_date, as: :date_picker
  end

  actions
end

ActiveAdmin.register User do
  index do
    column :id
    column :name

    actions defaults: false do |user|
      item I18n.t('active_admin.view'), manage_user_path(user), class: 'view_link member_link'
      item I18n.t('active_admin.edit'), edit_manage_user_path(user), class: 'edit_link member_link'
      item I18n.t('active_admin.delete'), manage_user_path(user), class: 'delete_link member_link'
    end
  end
end

ActiveAdmin.register Campaign do
  # delete アクションを追加
  # delete_manage_user_path が route に追加される
  member_action :delete, method: :delete do
    user = User.find params[:id]
    user.touch(:deleted_at)
    redirect_to manage_user_path, :notice => "Deleted!"
  end

  index do
    column :id
    column :name

    actions defaults: false do |user|
      item I18n.t('active_admin.view'), manage_user_path(user), class: 'view_link member_link'
      item I18n.t('active_admin.delete'), delete_manage_user_path(user), class: 'delete_link member_link', method: :delete, data: { confirm: I18n.t('active_admin.delete_confirmation') } # クリック時に confirm も表示させた 
    end
  end
end